The present invention relates to an optical transmission line glass and its method of manufacture.
An optical transmission line or optical fiber used as a transmission line for optical communication must have an extremely low impurity content, since such impurities deteriorate optical transmission characteristics.
A well known method of obtaining extremely pure glass material is one in which the fine powder of the glass forming oxide, or soot, is produced by the use of a gas phase chemical reaction. The soot is then vitrified and spun into glass fiber. In this method, since a compound of high purity, such as, for example, silicon tetrachloride (SiCl.sub.4), germanium tetrachloride (GeCl.sub.4), used in the manufacture of semiconductors, may be used as the raw material, extremely pure glass soot may be obtained only if the other reaction gases such as, for example, oxygen and hydrogen, are pure. However, the method of manufacture utilizing existing gas phase chemical reaction, as hereinbefore explained, uses a glass tube or glass rod as a support in order to permit the soot to stick to the inside wall of the tube or around the outside surface of the rod. This method is thus not suitable for mass production. Furthermore, in the known method hereinbefore described, soot consisting primarily of silicon dioxide (SiO.sub.2) is generally produced. Such soot has a usually high vitrifying temperature and the disadvantage that the vessel is corroded when vitrification is carried out in a silica vessel. On the other hand, if a vessel of metal such as, for example, platinum, is used instead of a silica vessel, the metal vessel dissolves into the glass material, distinctively deteriorating optical characteristics of the glass.
The principal object of the invention is to provide optical transmission line glass having excellent optical characteristics.
An object of the invention is to provide optical transmission line glass of few ingredients which is non-alkaline and has excellent optical characteristics.
Another object of the invention is to provide optical transmission line glass which is non-alkaline.
Still another object of the invention is to provide optical transmission line glass which is vitrified at a comparatively low temperature.
Yet another object of the invention is to provide optical transmission line glass having excellent waterproofing characteristics.
Another object of the invention is to provide optical transmission line glass which is vitrified in a silica vessel, which it does not corrode.
Still another object of the invention is to provide a method of manufacture of optical transmission line glass in which a volatile acidic oxide is mixed in the gas phase with a compound of an element which combines with such oxide in the gaseous state or gas phase and then oxidized to produce a bi-compound.
Yet another object of the invention is to provide a method of manufacture of optical transmission line glass in which glass fiber is spun by vitrification in a silica vessel and then drawn from a hole provided at the bottom of the vessel.
Still another object of the invention is to provide a method of manufacture of optical transmission line glass, which method is efficient and suitable for mass production.